Thermal comfort is a condition of mind that expresses satisfaction with a thermal environment and is assessed by subjective evaluation. Maintaining the standard of thermal comfort for individuals within a space, for instance, occupants of a building or other enclosure such as a vehicle, continues to be an area of research.
Thermal neutrality is maintained when heat generated by an individual's metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. The main factors that influence thermal comfort are those which determine heat gain and loss, mainly metabolic rate, clothing insulation, air temperature, mean radiant temperature, air speed and relative humidity. Psychological parameters such as individual expectations also affect thermal comfort.
Oftentimes, one or more individuals of a plurality of individuals within a space may be too hot or too cold, regardless of whether other individuals may be comfortable. This phenomenon is based, in part, on the personal temperature preferences of the individuals, in combination with, for instance, activities that the individuals are currently or recently engaged. Age and physical condition of the individual may also play a factor in thermal comfort at a given temperature. For instance, temperature which may feel comfortable for a young person in a healthy state, may seem too hot for a person with extra weight or with one or more ailments. Similarly, a comfortable temperature for a younger individual may be too cool for an older individual. In addition, even at an individual level, reaction to temperature can differ for a variety of reasons. For instance, a temperature which is considered hot in the summer may cause the same individual to feel cold in the winter. Thermal comfort, or temperature perception, may thus vary from individual to individual, and universally comfortable climate conditions may be difficult to achieve within a space.